Heart of Darkness
by Riverfury
Summary: Natsu and the others return after seven years to find that Fairy Tail has added a new member to its ranks. AU.
1. Chapter 1

It was good to be home, even if the building was different. His friends were here, and that made it home. Not that they hadn't changed. Romeo was big now, a teenager, and Bisca and Alzack had finally gotten married after dancing around each other for years. And there were new people in the guild now. Asuka, for one, Bisca and Alzack's kid who, if she hadn't taken the mark yet, was still a de facto member. And over in there in the corner, two unfamiliar people, glaring at each other over a short table and arguing animatedly about something that was almost certainly boring.

There was cheering, and celebration, and someone immediately called for a party, and then five different people headed off towards town to get supplies. Of course, no one bothered waiting for them to get back to start.

Natsu eventually found himself in the corner next to the two new members. He collapsed into the vacant chair, panting and grinning. Gajeel hadn't gotten stronger, but he'd hardly gotten weaker. It was only then that he took a proper look at the two men.

One of them was simply huge. He looked half-wild, with dark blue hair that was even more of a mane than Gajeel's, blue eyes so light as to be colorless, and dark skin, a rarity in Fiore. Light blue tattoos framed his face and disappeared down into the neckline of his strange black robe. There was something familiar about the eyes and the tattoo's, and even the man's scent, but Natsu couldn't quite place it. Surely he would have remembered if he had seen the man before?

The other was the first's near opposite, slim and slender and small with an innocent child's face. The black robes he wore hung from his body, as though he were all skin and bones underneath for all that his face looked healthy. He was wearing a necklace of some kind, with a single stone, but all Natsu could really focus on was his face.

The Dragon Slayer leaned forwards, hissed, "What the hell are _you_ doing here?"

The conversation between the two ceased. Both heads turned to look at him. Natsu felt as though he were simultaneously being stared down by a predator and sucked into a vortex.

"Damn it," the huge man grumbled, looking away. "It's my own fucking fault, of course. Well, punch me if I ever get hopeful again, yeah?" The last was to Zeref, who laughed quietly.

"Natsu," the boy who was not a boy said, "I joined four years ago. I am a member of Fairy Tail."

"Like hell you are!" Natsu snarled, and lunged across the table, fire magic already coalescing around one fist.

Which was caught by another hand, and squeezed so tightly that the dragon slayer almost gasped aloud in pain. The big man was standing, had Natsu's in an iron grip. The burning magic flaring from Natsu's skin didn't seem to bother him at all.

"Back off, Dragon Slayer," the man said, each word carefully enunciated. For all that he was practically crushing Natsu's hand, there was not even a hint of malice in his tone. He seemed... bored.

Natsu opened his mouth instead. "Fire Dragon's Roar!"

When the smoke cleared, the table was in smoldering pieces upon the ground, as was half the wall. Zeref had somehow leaped clear and was a few feet away, rising from a slight crouch, the fingers of one hand flicking in apparently random patterns in the air before him. The large man was nowhere to be seen. Good.

Natsu started towards Zeref, and only then noticed that the guild had grown deathly quiet. Everyone was staring at him, with a mixture of expressions. Some were resigned—Erza's, Lucy's, Makarov's—and others were... fearful? No, that wasn't quite right. More like worried. Max in particular looked almost frantic.

The Dragon Slayer turned around, faced his comrades. "What're you all so worried about?"

A moment later, a fist smashed him in the side of the head, and he found himself flying through the air, all the way across the room, to slam into the opposite wall. He rolled to his feet, coughing and rubbing his head. "What the hell...?'

The large man strode across the room, his teeth slightly bared. His _sharp_ teeth, every one looking as though they would be a better fit for a wolf's mouth. He had claws, too, black, twisted things sprouting from the tips of his fingers. Did he have Take Over magic?

Natsu quickly scrambled to his feet, drew himself up into a crouch. "Fire Dragon's-" he began.

The kick caught him the side of the chest, and he was flying through the room for the second time that day. How could the other man be so _fast_? Surely someone that big shouldn't be able to move so _fast._

Natsu staggered to his feet this time. His vision swam, maybe he had banged his head? Everyone was still staring at him... staring at him and the man approaching him. He felt... scared. He hadn't even seen the man move that last time, and if the other really _did_ have Take Over magic then he was more powerful still.

"Stop it." The quiet command came from the other side of the room. The large man's head instantly swung around, until his eyes lighted on Zeref who calmly walked towards him. The large man scowled, opened his mouth. "I mean it, Null," Zeref said, and there was just the barest hint of a threat in his voice, now. "It is hardly the first time I have been attacked. And I deserved it, in any case."

The large man—Null?-closed his eyes, sighed. "Always ruining my fun, little brother." And then he turned and stalked off, and when Natsu next looked at his hands they were back to normal.

Zeref offered him a hand up, and Natsu hesitantly took it. That seemed to be the cue for everyone to start talking at once, and Natsu saw both Erza and Makarov headed in his direction. Zeref evidently saw them too, because he stiffened slightly.

"Why did you help me?" Natsu asked warily.

Zeref eyed him. "I doubt you would believe me if I were to tell you."

"Try me."

"I am sick of death," the wizard said simply. A sad smile crossed his face, an expression present more in his eyes than in his mouth. "I am tired of causing death, and of bringing it to those around me. He would have killed you, you know. It is what he does. As it is what I do, but he is... more strongly bound to his nature, than I am to mine."

That hardly seemed like an explanation to Natsu, and the Dragon Slayer didn't really believe it. But he had no time to ask any further questions, because just then Makarov and Erza reached them.

"What the hell was that?" Erza growled, thumping Natsu's already tender head. "We've barely got here and already you're picking fights?"

"It was my fault," Zeref said softly. "You should not blame him. I do not believe we have met, ma'am." He offered his hand.

Erza hesitated half a second before taking it. "Erza Scarlet," she said.

The wizard nodded. "Zeref," he said simply, and then watched to see the two's reaction.

It was rather less explosive than Natsu would have predicted. Erza and Makarov both stared at him for a long moment. For some reason, Makarov didn't look surprised. "You're a part of the guild, aren't you?" Makarov asked as though he already knew the answer.

Zeref nodded. "I will understand if you want to kick me out."

The Master gave him a long stern look, as though he were actually considering it, then shook his head and broke out into a broad smile. "Naw, wouldn't think of it. The other guys already know, don't they? Yeah, they'd have to, or you couldn't have joined the guild. So if they're fine with you being in, then I'm fine with it."

There was shock in Zeref's expression and... were those tears? "Thank you," he whispered, and Natsu had never heard such sincerity. "Thank you."

Makarov shrugged, obviously uncomfortable.

"What are you doing?" Natsu cried. Zeref may have helped him out once, but he had also tried to kill him before, so that hardly made them friends.

"Natsu!" Erza said sharply. "He is the Master of this guild, and he has made his decision. What are you _thinking,_ Master?"

"Well," the diminutive man said. "I've been talking with some of the others about you, and from what I've heard you and your companion have been helping out a lot. Alzack said that you found and returned Asuka when she went wandering off. Max said there was this other guild called Twilight Ogre that had been harassing them, but you and your companion ran them off, and they didn't dare bother Fairy Tail after that. You've been looking after my family while I was gone. That means a lot."

Zeref said gently, as though explaining to a child, "I am _evil,_ Master Makarov. I caused more death and destruction during the Dragon War than anyone else. Someone who does that, even for the purest of causes, cannot help but be evil."

Makarov shook his head. "No, Zeref. You're not evil."

"I can't believe I'm hearing this," Natsu muttered. Erza hit him again.

"Evil is not what a man is," Makarov continued. "Evil is what a man does. And protecting Fairy Tail is not the action of an evil man."

"I would like to believe that," Zeref said softly. "Maybe one day I will be worthy of the faith you have in me."

"Hey," Null rumbled from behind Natsu. The Dragon Slayer jumped, and came down ready to fight. But the large man ignored him, spoke directly to Zeref. "I gotta fly. Business."

Zeref grimaced. "You need me?"

"Not this time, thank the gods. Good luck on the research, though I still say you're looking at it in entirely the wrong fucking way. No matter. I'll be back in a couple of weeks. Probably."

Zeref nodded, and that was evidently enough of a farewell, because the big man turned and walked away. The other members of Fairy Tail gave him a wide berth, Natsu noticed.

"What's his story?" Natsu demanded. The guy was inhumanly fast.

"He is my friend," Zeref replied calmly.

"I could swear I've seen him before."

Makarov said, "I get that feeling around him, too." Erza nodded.

"He is my friend," the black wizard repeated. "No, Master Makarov, he is not a member of Fairy Tail. He was asked, but he never joined."

They pressed for more, but Zeref's lips were sealed.

 _I don't trust you,_ Natsu thought, staring at the boy who was not a boy. _And I don't trust your companion either. I'll be watching you._


	2. Chapter 2

Natsu did his best to watch Zeref during the resulting welcome back party, and only partially succeeded, due in no small part to Gray's continued idiocies. The only information he noticed, though it certainly wasn't exactly useful, was that Zeref mostly kept to himself and seemed to spend an inordinate amount of time staring into space while apparently doing nothing.

In short, Natsu was bored. He had decided to watch Zeref for the good of the guild and all, but the black wizard wasn't _doing anything._ He half-wished that Zeref would try to kill them all or something just for some excitement. He was starting to think that maybe the other wizard was actually telling the truth—after all, how much could you really accomplish just by sitting absolutely still all day?

The man was just _boring._ Watching him was boring. On the second night, Natsu had successfully tracked him when he left the guild, and discovered that Zeref spent his nights hanging in a hammock from a tree. He was pretty sure that the dark wizard had known that he was being followed, but he hadn't said or done anything, and eventually Natsu got bored enough that he just went home.

Still. Zeref was up to something, he just knew it. He wasn't going to drop his guard just because the man refused to do anything interesting.

And then everyone started talking about the Grand Magic Games, and how Fairy Tail should enter. Normally, Natsu would have been excited about this, especially the chance to prove to everyone that Fairy Tail was still a guild of consequence. Apparently, while Zeref had protected the guild from Twilight Ogre, he hadn't ever gone on any jobs, and so Fairy Tail had rapidly fallen in standing. This new guild called 'Sabertooth' was now ranked at the top, and ordinarily Natsu would have been all fired up to knock them off.

But he just couldn't work up the excitement, not when being around the dark wizard on such a daily basis was leaving him constantly on edge.

"I really don't think he's all that bad," Wendy said to him on the second day. Natsu hadn't exactly been discreet in his staring, after all, not that Zeref seemed to notice, or care. "He's been here for years without hurting anyone after all... people can change. Gajeel and Juvia did."

"Gajeel and Juvia never did anything like him," Natsu growled back, and stalked off. Compassion was all very well, and usually it was the best response to any given situation, but someone as evil as Zeref surely didn't just _decide to be good._

When the explosion finally happened, he felt vindicated. Unfortunately, it was a small explosion that didn't affect anything but Zeref's corner. Natsu turned his head to see a copious amount of black smoke completely obscuring the black wizard's figure, who seemed to be coughing violently.

"I hate it when he's right," Zeref said simply when the smoke mostly cleared. He looked down at the blackened tabletop and cautiously poiked it with one finger. It crumbled away into ash. "Sorry about that; I'll make another one."

Most of the old members had already turned away, going back to their fights or their food or their books, evidently used to such explosions, but everyone who had gone to Tenroujima was staring at him.

"Your hand," Lucy said tentatively. "It's rather... charred."

Zeref eyed his right hand as though seeing the blackened flesh for the first time. "It is, isn't it." He lifted it experimentally, and it dangled limply from his wrist. One finger twitched, and then was still.

"I could heal it, if you want," Wendy said, looking nervous, but determined. Natsu frowned at her but said nothing. Zeref was unlikely to hurt her for offering to help him.

Wendy stood and left Natsu's table, walking towards Zeref as the rest of the guild returned to their conversations or, in the case of Cana, their drinking. After all, explosions were quite commonplace in Fairy Tail, and it looked as though nothing so interesting as a fight was going to take place.

The fire dragon slayer followed Wendy over to the burnt remnants of the table, stopping a few feet away so he could listen without being _too_ conspicuous. Zeref's eyes flicked towards him before returning to rest on Wendy.

"My magic," the girl said, more quietly. "It lets me heal. That looks really painful..."

Zeref blinked up at her, then said sincerely, "That really is very kind of you. Thank you. Especially since you were on Tenroujima... really, thank you. But... best not to, I think. Our magics are sufficiently opposed that they would react rather negatively, and usually in cases like this the darker magic is the one that comes out on top. Besides, I think I burned all the nerves away, so it actually does not hurt all that much. Of course, in five or so minutes those will be repaired..."

Wendy's eyes widened. "Oh... I see. Is there any way I could help, though? I think I could probably just take away the pain, that doesn't take _that_ much magic."

"Any application of magic creates a... link, sort of. But again, thank you for the offer. You are a good person, really." Zeref stood and looked at the ruined table. "I suppose I had best get started on building another one... I think I can probably build it without a brain, if I try hard enough."

Wendy decided to ignore this. "Are you sure there's nothing I can do? You seem kind of lonely, sitting over here all by yourself. Even Bisca and Alzack and those guys never really come over to talk to you. I mean, Natsu obviously thinks you're evil and all, and I think a lot of other people do as well, but... you haven't done anything yet that screams evil, and I understand that you were locked away for four hundred years... that long of a confinement can really change a person."

Zeref snorted. "Not evil... don't delude yourself. What I have done since breaking free has not even begun to balance out everything else. I am a _killer,_ Wendy."

She shook her head, and refused to back down. "People can change. And even if you've done some really horrible things in the past, well you're trying to make up for it, aren't you?"

Zeref grimaced. "I suppose. I think I'm on the point of giving up on that, though."

Wendy froze, and Natsu immediately started paying closer attention. "What?" they asked simultaneously.

The black wizard glanced at Natsu briefly before returning his gaze to Wendy. "Nothing can kill me, I'm afraid. Well, it is possible that Null could, but I could never convince him to do so. The only way I could possibly pay for what I have done is with my death, and that has never happened, no matter what I have tried."

"That's not...!" Wendy rested her hands on her hips and glared. "That's not the right way to go about it at all! Dying? You think dying would fix anything? Dying... dying is the coward's way out!"

"Brave words... your mother would be proud." And he turned to leave.

"My mother?" Wendy whispered. She hurried after him, grabbed his shoulder, ignoring his resulting flinch. "You know my mother?"

"Not really," Zeref said, shrugging her off and continuing walking. "We have talked once or twice, but my control was nowhere near as good in those days, and she stopped trying to fix me after I inadvertently tried to kill her."

"Do you know where she is?" Wendy demanded, ignoring the comment about nearly killing her for now. She could be upset about that later, she had to know _this_ now.

"As far as I know, she is still alive. As to where she is... I have been informed that my 'puny human mind' could not possibly understand the answer to that question, as it involves moving through higher dimensions and the use of more copious amounts of magic than even I could handle."

"If you're hiding anything," Natsu began. "I swear I'll-"

"I wish you could." They left the guild building and continued on toward the forest. "I truly do. Even if I knew how to get you there, though, I would not take you. They would kill you for it."

"Do you know who can?" Wendy asked. "Please, if there's any way we can see our parents again..."

"Any dragon could."

"Acnologia..." Natsu murmured. "Could Acnologia take us?"

"He is a dragon, isn't he?" Zeref shook his head. "But you should give up on that particular thought. He would never deign to take you there, even if he let you get out your request before he ate you."

"Then we'll just have to make him!" Natsu said triumphantly. "I mean, we've got a bunch of dragon slayers here, and, well, if we all trained really hard..."

Zeref paused, looked back at them. "Trust me. You couldn't." His face twisted into a brief grimace, and he looked down at his mangled hand, muttering something under his breath, before turning and heading into the forest.

Natsu and Wendy watched him go. "I wish there was a way I could see mother again," Wendy murmured. "Even if just for a little while." She looked up at Natsu. "We have to try, don't we?"

"I've been looking for my dad my whole life, ever since he left me," Natsu said quietly. "I always... always just wanted to ask him, 'why?' I can't give up on the chance to talk to him."

"Come on," Wendy said. "Let's go tell the others."

Zeref leaned back against a tree, closing his eyes and cradling his hand in his lap. The pain was starting to fade as his flesh repaired itself. A pity that it couldn't happen more quickly, that since he had been the one to hurt himself in the first place it took longer to heal... Well. It was his fault for being careless.

"Zeref?" asked an achingly familiar voice.

He stopped breathing for a moment. That voice... no, it was impossible. She was dead. He had seen her die. He had felt her flesh cooling under his hands, had felt her heart stop. He had never had hallucinations before, but perhaps there was a first time for everything.

"Zeref," the voice said again, a bit of impatience in her tone. "Aren't you even going to look at me?"

He opened his eyes, and stared up into _her_ face. She was, he noted, floating an inch or so above the ground and seemed slightly transparent, but it was her. That was her face, her hair. She was still wearing the same dress as the night she had died.

"You're dead," he said, and the words came out as a croaking whisper. "I saw you die."

"Yes," she said, and drifted closer. "I've seen you die, too. You're still here."

"It's... it's really you?" he asked, then.

"It's really me. Someone brought back my spirit, years after you killed me." Her voice held no judgement, no anger, but Zeref still flinched.

"I didn't mean to," he said, and looked away. "I really... really didn't mean to."

"I know," she said. "It's alright. Neither of us were thinking clearly that night."

Zeref smiled bitterly and said nothing. Yes, that was one way to put it. Gods, he had been so _young_ back then, so headstrong and arrogantly sure of himself and his control. If he had only thought a little more, had waited or warned her... things could have been so different.

"Zeref," she said again, her green eyes full of far more compassion than he deserved. "Don't blame yourself. It was an accident, that's all." He said nothing. She sighed, then said, "When you called him, did you know what you were doing?"

He looked up sharply at her. "What?"

"When you called Acnologia. On Tenroujima. I don't think they," she waved one hand vaguely in the direction of the guild house, "have figured it out yet, but it's rather obvious that it was you, if you think about it. I never met him, but I heard stories. He would never come into the human world on his own."

"No," Zeref said honestly. "I was... a mess. I didn't even know my own name. In that moment... I had just killed someone, someone who was trying to kidnap me, and I was scared. And this name just popped into my head, and I said it, without even thinking. I had forgotten all about it by the time I was leaving the island on that ship, and by then it was too late."

She nodded. "That's what I thought. I don't think the guild will see it that way, though, so you had best be careful."

A mischievous gleam suddenly came into her eyes. "So, what can I do to convince you to participate in the Grand Magic Games?"


End file.
